Recently, Britain's health secretary Matt Hancock suggested that “Immunity certificates” may be issued to people who have immunity against COVID-19. The hope is that by identifying people who have already had the coronavirus, they can return to work and help kick off the economy again.
Despite a scientifically sound rationale behind immunity certificates, the nature of immunity against coronavirus is still not far from clear.
Normally, when your body meets a virus, the immune system quickly rings the alarm bell and sends off immune soldiers like the white blood cells to get rid of the invader. From the initial infection, the immune system may “remember” how to protect against the same virus in a future infection.
The immune system uses an “antibody” to recognize a specific invader, or “antigen”. We exploit this natural response in vaccination to stimulate the body to produce antibodies, and therefore, protective memory.
While higher levels of antibody in the blood usually means a higher immunity, they don’t always mean full protection. Someone may develop partial immunity that would not prevent them from another infection, but could protect them from severe symptoms.
In addition, it is possible that someone with COVID-19 antibody can still carry the virus and pass it onto others, despite being immune themselves. If COVID-19 mutates at a fast rate like the seasonal influenza virus, being immune to the initial COVID-19 outbreak also doesn’t protect people against the second or third wave.
Every virus is different, and we are learning more about this new enemy at the same time as our immune system. A small preliminary study from China just found that some of the recovered patients developed antibodies, whereas others did not. Researchers don’t yet know what causes this individual difference.
Professor John Newton, a professor at Public Health England has said that “I think we have to be optimistic that it will give some immunity, but we’re just not quite sure how much at the moment.”
The best scenario is a lifetime immunity, similar to the case of polio, whereas the worst case scenario is a short, partial immunity. This immunity could last a month, a year or ten years, we just don’t know.
Hopefully, we will soon be able to update you answers to questions like:
- If we do develop immunity to COVID-19, how long is it going to last?
- To what extent can high levels of antibody protect someone from re-infection?
- Will the virus mutate to a new form that evades the immune system’s protective memory?
- Can people who are “immune” to COVID-19 still pick up the virus and transmit to others?
- What determines if someone develops high, low or undetectable antibody levels?
Until then, please continue to follow the best practices that protect you against COVID-19!